U.S. patent application number 10/574879 was filed with the patent office on 2007-11-29 for contact surfaces for electrical contacts.
Invention is credited to Volker Haas, Peter Rehbein.
Application Number | 20070275611 10/574879 |
Document ID | / |
Family ID | 34399256 |
Filed Date | 2007-11-29 |
United States Patent
Application |
20070275611 |
Kind Code |
A1 |
Rehbein; Peter ; et
al. |
November 29, 2007 |
Contact Surfaces For Electrical Contacts
Abstract
A contact surface for electrical contacts may include an Ag
layer deposited on a copper-based substrate using galvanic methods.
The Ag layer includes finely dispersed graphite particles in a
quantity of, e.g., 1 to 3 weight % of the Ag layer, the graphite
particles having a length in the range of, e.g., 0.5 to 20
.mu.m.
Inventors: |
Rehbein; Peter; (Weissach,
DE) ; Haas; Volker; (Tamm, DE) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
34399256 |
Appl. No.: |
10/574879 |
Filed: |
August 3, 2004 |
PCT Filed: |
August 3, 2004 |
PCT NO: |
PCT/DE04/01733 |
371 Date: |
January 19, 2007 |
Current U.S.
Class: |
439/886 |
Current CPC
Class: |
Y10T 428/12486 20150115;
Y10T 428/12493 20150115; Y10T 428/12896 20150115; Y10S 428/929
20130101; Y10T 428/12625 20150115; Y10T 428/265 20150115; H01R 4/58
20130101; Y10T 29/49224 20150115; Y10T 428/12903 20150115; Y10S
428/935 20130101; Y10T 29/49204 20150115; H01R 13/03 20130101 |
Class at
Publication: |
439/886 |
International
Class: |
H01R 13/03 20060101
H01R013/03 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2003 |
DE |
103 46 206.6 |
Claims
1 to 8. (canceled)
9. A contact surface for an electrical contact, comprising: an Ag
layer galvanically deposited on a copper-based substrate, the Ag
layer including finely dispersed graphite particles in a quantity
of between 1 and 3 weight % of the Ag layer, the graphite particles
having a length in a range of 0.5 to 20 .mu.m.
10. The contact surface according to claim 9, wherein the graphite
particles have a length in the range of 1 to 10 .mu.m.
11. The contact surface according to claim 9, wherein the graphite
particles have a thickness in the range of 0.05 and 2 .mu.m.
12. The contact surface according to claim 9, wherein a ratio of
thickness to length of the graphite particles is in the range of
1:2 to 1:40.
13. The contact surface according to claim 9, wherein the graphite
particles are arranged at least one of (a) anisotropically and (b)
statistaically along a habitus plane of the Ag layer.
14. The contact surface according to claim 9, wherein a layer
thickness of the Ag layer is in the range of approximately 1 to
approximately 10 .mu.m.
15. The contact surface according to claim 9, wherein the graphic
particles do not simultaneously include a maximum thickness and a
maximum width.
16. A contact surface for an electrical contact, comprising: a
copper-based substrate; and an Ag layer galvanically deposited on
the copper-based substrate, the Ag layer including finely dispersed
graphite particles in a quantity of between 1 and 3 weight % of the
Ag layer, the graphite particles having a length in a range of 0.5
to 20 .mu.m.
17. A method, comprising: providing a contact surface in an
automotive plug connection in close proximity to an engine, the
contact surface including an Ag layer galvanically deposited on a
copper-based substrate, the Ag layer including finely dispersed
graphite particles in a quantity of between 1 and 3 weight % of the
Ag layer, the graphite particles having a length in a range of 0.5
to 20 .mu.m.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to improved contact surfaces
for electrical contacts.
BACKGROUND INFORMATION
[0002] Electrical connectors such as bushings and plugs are
typically produced from a substrate made of an alloy on copper
basis, which provides good electrical conductivity. If the
electrical connector is exposed to higher temperatures during
operation, such as under the engine hood of a motor vehicle, the
substrate is made from an alloy on copper basis having high
stability and a high strain-relaxation resistance.
[0003] A cover layer is often applied on the substrate to reduce
tarnishing of the copper-based substrate at higher temperatures and
to improve the soldering ability. Typical cover layers are made of
nickel, palladium/nickel alloys, tin or tin alloys. To minimize
costs, tin is often used, predominantly fire-tinned or galvanically
deposited layers in the range of a few .mu.m. Tin is characterized
by its ductility and its excellent electrical conductivity.
[0004] The substrate is usually made of copper-based alloys such as
CuSn.sub.4-bronze, CuNiSi, etc., which often serve as base material
for electrical plug-in connections. At higher temperatures it may
happen that copper diffuses out of the substrate and combines with
the tin, forming intermetallic compounds such as Cu.sub.6Sn.sub.5
and Cu.sub.3Sn. The formation of such intermetallic compounds
reduces the quantity of unreacted or free tin on the surface. This
has a detrimental effect on the electrical, corrosion and other
performance characteristics.
[0005] A "tin layer" produced by heat treatment is referred to as
thermo-tin, which is made of intermetallic phases to 100%. Also
frequently used are AuCo alloys having nickel undercoating, and Ag
surfaces, partly having copper undercoating or nickel
undercoating.
[0006] So far, however, thermo tin has not shown to be a successful
solution in all test situations (such as chemical testing or
abrasive loading), and therefore has no more than a very small
marketing share.
[0007] Moreover, it is conventional that tin alloys, due to their
low hardness or their low wear resistance, have a tendency to
increased oxidation (chafing corrosion) and to abrasion as a result
of frequent plug-ins or vehicle-related or engine-related
vibrations in the plug connector. This abrasion or chafing
corrosion may lead to malfunctioning of a component (sensor,
control unit, electrical components in general).
[0008] In addition, due to the high adhesion tendency and the
plastic deformation, the plug forces are too high for many
application situations such as plug connectors having a high number
of (poles, e.g., >100 pins or contacts). Surfaces on the basis
of tin and silver, in particular, have a cold welding tendency
because of adhesion, and in self pairings are characterized by high
friction values (coefficients of friction).
[0009] Even with conventional silver or gold layers, tribological
wear mechanisms of the base material or the intermediate layer
(frequently Cu or Ni) may occur with layer abrasion or layer
chipping, due to poor adhesion.
[0010] EU directive "Altautorichtlinie" 2000/53 forbids the use of
lead-containing tin layers. Since the lead inhibits whisker
formation (whiskers are tiny, hair-like crystals), galvanic pure
tin promotes whisker growth, which may lead to short-circuits.
[0011] In U.S. Pat. No. 5,028,492, a composite coating for
electrical contacts is described, which includes a ductile metal
matrix and a uniformly distributed polymer component. The polymer
component is present in a concentration that reduces the frictional
forces that occur when a contact is inserted into a corresponding
receptacle. The composite coating provides lower friction and
improved frictional oxidation compared to a galvanically deposited
tin coating.
[0012] U.S. Pat. No. 5,916,695 describes an electrical contact
having a copper-based substrate, which has been provided with a
tin-based cover layer. To prevent diffusion of the copper from the
substrate into the cover layer and the attendant formation of
intermetallic layers, a barrier layer is applied between the
substrate and the cover layer. This barrier layer contains 20 to 40
weight % of tin and preferably is mostly made up of copper (Cu
base). Among others, the tin-based cover layer may include
additives such as SiO.sub.2, Al.sub.2O.sub.3, SiC, graphite or
MOS.sub.2 as lubricants.
SUMMARY
[0013] In contrast to the foregoing, the contact surfaces according
to example embodiments of the present invention may provide that
they require low plug-in forces while still supplying excellent
electrical contacting.
[0014] Moreover, it may be provided that they protect the surface
from corrosion due to the antioxidants contained in the
lubricant.
[0015] Furthermore, increased wear protection and thus of an
increased service life of the contacts may be provided.
[0016] Example embodiments of the present invention are described
in greater detail below with reference to the appended FIGURE.
BRIEF DESCRIPTION OF THE DRAWING
[0017] The FIGURE illustrates the arrangement of the graphite
particles in an Ag contact layer.
DETAILED DESCRIPTION
[0018] Example embodiments of the present invention provide for the
construction of an Ag cover layer, which has finely dispersed
graphite particles embedded therein, on a copper-based substrate
for electrical contacts in the automobile, which may require lower
plug-in forces while providing the same satisfactory
contacting.
[0019] As illustrated in the FIGURE, an Ag contact surface 12 is
first produced on the electrical contact, i.e., on copper-based
substrate 10, using galvanic methods such as baths or reel-to-reel
methods.
[0020] The Ag layer may be deposited with or also without
intermediate layers as diffusion barriers, such as a tin
undercoating, and also with or without flash of noble metals such
as Au, Pt, Ru or Pd.
[0021] The layer thickness of the deposited Ag layer may be between
approximately 1.0 and approximately 10 .mu.m, depending on the
application.
[0022] Finely dispersed graphite particles 14 are introduced into
the Ag layer, for example, by intermingling of graphite and
chemical auxiliary agents for binding (wetting agent), the graphite
quantities being in the range of, e.g., 1 to 3 weight % of carbon
of the Ag layer, or in the range of, e.g., 3 to 10 surface % of
carbon. The graphite particles may be present as platelets or
flakes and have a length of, e.g., between 1 and 10 .mu.m, a
thickness, e.g., in the range of 0.05 to 2 .mu.m, and a width,
e.g., in the range of 0.05 to 2 .mu.m. It may be provided that the
maximum value for thickness and width, i.e., 2 .mu.m, does not
occur simultaneously. The graphite particles may be disposed
anisotropically along the habitus plane of the Ag layer, i.e.,
along the longest axis of the layer plane (cf. the FIGURE).
[0023] The aspect ratio of the graphite particles, i.e., the ratio
of length to thickness, may be, e.g., 1:2 to 1:40.
[0024] The contact surfaces may allow lower plug-in forces as a
result of the included graphite lubricant. Good contacting may be
ensured by the electrical conductivity of the lubricant.
Antioxidants included in the lubricant protect the surfaces from
corrosion, thus providing high wear resistance and a high number of
plug-in cycles.
[0025] The contact surfaces may be used in electrical contacts in
automotive plug connections that are in close proximity to the
engine.
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